Hospital beds are characterized by adjustment of the head and foot with lift means which elevate the head and foot portions of the springs and mattress respectively. Basically, this type of bedding is mechanical with hand operated cranks, with the availability of similar systems that operate electrically and hydraulically. However, the greatest need arises in the basic manually operated bed to be converted and automated so that the invalid can conveniently power operate the same, and to this end it is a general object of this invention to provide a motor powered adapter unit for operating the lift screws of such beds.
The normal hospital bed comprises a frame with articulated head and foot sections that are raised from a horizontal plane by means of manually operable lift means. In practice, there is one lift means along one bed rail to raise and lower the head portion, and one lift means along the other bed rail to raise and lower the foot portion. In the manual version, the lift means for the head and foot are substantially alike and comprised of hand cranked screw jacks operating levers that raise and lower the mattress supporting frame sections. A characteristic feature of these hospital beds is the cover tube that extends over the engageable end portions of the screw shafts, normally engaged by a swivel handle or crank. There are two general types of handle or crank couplings, the handle version which comprises a transverse pin extending between opposite sides of a slotted screw shaft for swivelled driving engagement with the handle, and the crank version which comprises a transverse pin projecting diametrically at opposite sides of the screw shaft for releasable driving engagement with a socketed hub of the crank. Either version is compatable with the present invention, the crank drive pin as is, and the handle drive pin removed and/or replaced with a crank drive pin as described above. Therefore, it is an object to provide modification of the screw shaft of the handle type, replacing the drive pins as necessary for coupled engagement with the sleeve coupler of the present invention.
The drive hubs of worm and gear actuators have been restricted in rotative angular displacement by limit switches and the like applied to the members actuated, and all of which requires limit means associated with the frame members of the hospital bed sections to be positioned. With the present invention it is an object to integrate such limit means, for varied angles of displacement, within the confines of the worm and gear actuator and associated directly with the drive hub, to operate limit switches at one or both ends of travel, as circumstances require. In practice, the worm is self locking with the gear driven thereby, and the drive hub is integral with the said gear and with a thread helix on the hub in constant mesh with a timing gear to which replaceable cams are keyed to actuate limit switches, one for each direction of travel.
The aforesaid worm and gear actuator and switch controlled limit means is enclosed in a single housing comprised of two half shells to which a drive motor is applied and which exposes the drive hub on bearings for coupled engagement with the screw shaft as will be described. A feature of adaptability is the mounting bracket that accommodates bed construction with either upper or lower cover tubes, a "crank over" bed being shown herein, where the cover shaft operates over the frame at either side of the foot of the bed (see FIG. 2). It is to be understood that there are "crank under" beds where the screw shaft operates in a cover tube disposed beneath the frame at either side of the bed foot, and to which the adapter unit of the present invention is equally applicable. It is an object of this invention to clamp the adapter unit to such tubes while embracing the transverse frame member at the foot of the bed, so as to secure the drive unit as such and to ensure the transmission of torque therefrom.